1. Field of the Invention
Embodiments of the invention relate to the field of microprocessors, and more specifically, to processor performance states.
2. Description of Related Art
Advances in microprocessor technology have provided users with high level of performance flexibility. For example, emerging processors have multiple performance state efficiencies. Device performance states typically trade device performance for a reduction in one or more of the following device parameters: power consumption, thermal operation, and acoustical characteristics. Performance policy is usually driven by multiple factors such as device activity or demand, power source, user preferences (e.g., performance, power savings, and acoustics), and adverse conditions (e.g., thermal conditions, low battery power).
The Advanced Configuration and Power Interface (ACPI) specification introduced a new method for performing platform power management and enumeration. The architecture is table-based and has the capability to execute control methods written in ACPI Source Language (ASL) code. The ACPI provides a standard specification from which a global power management may be developed. This global approach, however, has a number of disadvantages. First, the model assumes that the OS knows the capabilities of and can control all the devices or processors in the platform. This is not necessarily true when newer devices are added to the platform. Second, the model cannot distinguish individual devices or processors in terms of power management. In practice, each device or processor may have different performance characteristics. Third, the model creates burden to provide various device drivers.